A plasma processing process and a plasma processing apparatus are indispensible technologies in manufacturing a recent micro semiconductor device having a gate length is near to, or equal to or below 0.1 μm, which is so-called a deep sub micron device or a deep sub quarter-micron device, or manufacturing a high-resolution flat panel display apparatus including a liquid crystal display apparatus.
The plasma processing apparatus used to manufacture a semiconductor device or a liquid crystal display apparatus uses any one of various conventional methods of exciting plasma, but specifically, a parallel plate type high-frequency excitation plasma processing apparatus or an inductively coupled plasma processing apparatus is generally used as the plasma processing apparatus.
However, since plasma formation is not uniform and a region having high electron density is limited in such conventional plasma processing apparatuses, it is difficult to perform a uniform process on the entire surface of a substrate to be processed at a high processing speed, i.e., high throughput. Such a difficulty becomes serious when a substrate having a large diameter is processed. Moreover, since an electron temperature is high in the conventional plasma processing apparatuses, there are several fundamental problems, such as generation of damage to a semiconductor device formed on a substrate to be processed, large metal contamination due to sputtering on a wall of a processing chamber, etc. Thus, it is difficult for the conventional plasma processing apparatuses to satisfy strict requirements for further miniaturizing and further improving productivity of a semiconductor device or a liquid crystal display apparatus.
Considering such problems, a microwave plasma processing apparatus using high-density plasma excited by a microwave electric field, not by a direct current magnetic field, has been suggested. For example, a plasma processing apparatus, which is configured to radiate a microwave from an antenna (radial line slot antenna) having a plurality of slots arranged to generate a uniform microwave and having a flat shape into a processing container, and excite plasma by ionizing a gas in a vacuum container according to the microwave electric field, has been suggested (for example, refer to Japanese Laid-Open Patent Publication No. hei 9-63793).
The microwave plasma excited via such a method may realize high plasma density throughout a wide region directly below the antenna, and thus it is possible to perform a is uniform plasma process in a short time. Moreover, the microwave plasma formed as such a method has a low electron temperature since plasma is excited by a microwave, and thus damage of a substrate to be processed or metal contamination may be avoided. Also, since uniform plasma can be easily excited even on a large substrate, the plasma processing apparatus can easily cope with a manufacturing process of a semiconductor device using a semiconductor substrate having a large diameter or a manufacturing process of a large liquid crystal display apparatus.
FIG. 1 is a cross-sectional view showing an example of a structure of a conventional microwave plasma processing apparatus.
A microwave plasma processing apparatus 10 shown in FIG. 1 includes a processing container 11 having a support 111 that supports a substrate to be processed S in the processing container 11, and a gas shower 12 and a gas introduction pipe 17 disposed in the processing container 11. The gas introduction pipe 17 is formed to penetrate through an inner wall 11B of the processing chamber 11 while being held by the inner wall 11B, thereby mainly supplying an inert gas for plasma generation into the processing container 11. The gas shower 12 is fixed to an inner wall of the processing container 11 by a jig that is not shown, and is configured to supply a gas for processing from a gas supply source that is also not shown into the processing container 11 through an opening 12A. Also, an opening 11A for connection to an exhaust system, such as a vacuum pump or the like, that is not shown is formed at the bottom of the processing container 11.
Also, a microwave antenna 13 is provided on the processing container 11 to vacuum-seal the processing container 11. A coaxial waveguide 14 extending perpendicularly upward is provided at about a center of the microwave antenna 13, and a coaxial converter 15 is provided at an end portion of the coaxial waveguide 14, which is of a side opposite to the microwave antenna 13.
The coaxial waveguide 14 includes an inner conductor 141 and an outer conductor 142, wherein an upper end portion 141A of the inner conductor 141 and an upper wall surface of the coaxial converter 15 are fixed by a screw 21, and an upper end portion 142A of the outer conductor 142 and a lower wall surface of the coaxial converter 15 are fixed by a screw 22. Accordingly, the coaxial waveguide 14 and the coaxial converter 15 are mechanically and electrically connected to each other.
The microwave antenna 13 includes a cooling jacket 131, a wavelength-shortening plate 132 provided to face the cooling jacket 131, and a slot plate 133 provided on a main surface, of the wavelength-shortening plate 132, which is of a side opposite to the other main surface of a side on which the cooling jacket 131 is provided.
Also, the cooling jacket 131, the wavelength-shortening plate 132, and the slot plate 133 are provided on a top plate 135 that is a constituent of the antenna 13. The top plate 135 is supported by an upper end portion of the wall surface 11B of the processing container 11. Also, although not specifically shown, the cooling jacket 131 is mechanically fixed to the upper end portion of the wall surface 11B by a screw or the like.
A lower end portion 142B of the outer conductor 142 of the coaxial waveguide 14 is fixed to the cooling jacket 131 by a screw 23. Accordingly, the coaxial waveguide 14 and the antenna 13 are mechanically and electrically connected to each other.
Also, the cooling jacket 131 is provided to cool down a top plate (microwave transmission window) or the like that is heated up by radiant heat or the like of plasma generated in the processing container 11, wherein a refrigerant flows inside a communicating hole 131A formed inside the cooling jacket 131. Also, a portion including the communicating hole 131A forms a cooling portion 131B.
Also, a lid 134 is coupled to a top surface of the cooling jacket 131 by a screw 24 by disposing an O-ring 28 on the top surface of the cooling jacket 131, and thus the communicating hole 131A is blocked by the lid 134.
Also, as shown in FIG. 1, an end portion 133A of the slot plate 133 is fixed to the cooling jacket 131 by a screw 26.
When treatment processing or the like of the substrate to be processed S installed on the support 111 is started by generating the plasma in the processing container 11, the antenna 13, specifically the top plate 135 is heated up to or above 100° C. by the radiant heat of the plasma. Accordingly, as described above, the antenna 13 needs to be cooled is down by the cooling jacket 131.
However, with respect to the cooling of the top plate 135 that is mostly affected by the radiant heat of the plasma, the cooling portion 131 B of the cooling jacket 131 and the top plate 135 are spaced apart from each other, and the wavelength-shortening plate 132 and the slot plate 133 are disposed between the cooling portion 131B and the top plate 135. Accordingly, original thermal resistance increases since the cooling portion 131B and the top plate 135 are spaced apart from each other, and at the same time, a gap may be generated between the wavelength-shortening plate 132 or the like and the cooling jacket 131 due to deformation of the wavelength-shortening plate 132 or the like and the cooling jacket 131 by the above-described radiant heat. Thus, the thermal resistance also increases due to such formation of the gap. As a result, it was difficult to sufficiently effectively and efficiently cool down the top plate 135 by using the cooling jacket 131. Prior Art Document
(Patent Document 1) Japanese Laid-Open Patent Publication No. hei 9-63793